Wikipedia:Reference desk/Archives/Science/2010 December 27

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December 27

Crocodile Dundee II

I know it's "just a movie", but I'm still curious: in "Crocodile" Dundee II, Dundee jumps off a building, holding a rope, and about five or six stories down, the rope snaps taught, and he swings right through a window. Assuming the rope could never break, would this stunt even be remotely possible, without ripping skin off one's hand, etc.? – Kerαunoςcopia^◁_galaxies 08:32, 27 December 2010 (UTC)

It presents a number of genuine difficulties so it would be reasonable to assume this stunt could not be achieved in real life, only in the composite world that can be achieved in film - shoot a number of different sequences, each one entirely ordinary, and then splice them together to give the audience the overwhelming impression that this extraordinary action is not only possible, but that it actually happened. Dolphin (t) 12:04, 27 December 2010 (UTC)

What is interesting is how close one could come, with a sufficiently stretchy rope, careful measuring, and careful training. But if you fall 5 stories down, and the rope "snaps" taught" , there are several g of acceleration involved, and you probably rip of some body parts. --Stephan Schulz (talk) 13:16, 27 December 2010 (UTC)

While we're being technical and nitpicky, "snapping taut" is a very hand-wavey description of what's actually happening. The rope is simultaneously undergoing several processes. First, it is undergoing a long-duration inelastic collision with the person (who is otherwise in freefall) and with itself (because, as we model it with continuum mechanics, a continuous distribution of infinitesimal connected rope pieces, each with their own infinitesimal mass, momentum, position, and so on). The duration of that collision is non-zero and in fact begins at the instant the jump begins. The rope is also compliant to some extent - even a very tough rope has some elasticity - so there is an elastic deformation (stretching) of the rope that also absorbs some of the energy of the fall. The best way to estimate the feasibility would be to consider the energy per unit time that the hands must absorb in order to remain attached to the rope. This is easy - consider the trajectory of the fall; model or measure the instantaneous velocity and position, and construct a power dissipation graph vs. time. If at any time during the fall, the hand must absorb more power than the material (skin) is able to withstand; or if its contact force is greater than the hand can sustain (this is a bit gross, but a human hand has a threshold before it starts to break or tear skin). If we allow the hand to slide (so that the man actually slips down the rope as he falls, in addition to swinging), we have more parameters to estimate - the contact force between hand and rope; the coefficient of friction; and the dissipated energy there. The point is, we could accurately model all of this, and come up with some realistic bounds for jump length, rope flexibility, hand strength, and so on; given these parameters, we could estimate a maximum amount of swing before the action movie scene goes from "dangerous / implausible" into the realm of "physically impossible." Nimur (talk) 16:41, 27 December 2010 (UTC)

It's really not all that difficult, if you have the rudiments of Rappelling down. Here is a short humorous video clip of a firefighter attempting to make a two-story controlled rappel-drop into a window. WikiDao ☯ (talk) 17:02, 27 December 2010 (UTC)

On the other hand, yes: it was just a movie, the main character of which is supposed to be capable of awe-inspiring feats like that as far as I know, I haven't actually seen it so I really shouldn't say. WikiDao ☯ (talk) 20:27, 27 December 2010 (UTC)

Problem 1: G forces. Solution: An elastic "rope". Also, don't hold onto rope directly, but use a harness that distributes forces over more than just your hands.

Problem 2: Too much downward force and upward rebound, and too little lateral force toward window. Solution: Don't jump straight down, but rather follow something closer to a circular arc, by running off the roof.

Problem 3: Hitting the window, not the wall. Solution: Careful planning, taking into account the elasticity and length of the "rope", and the exact location, speed, and direction on which one leaves the roof.

Problem 4: Getting sliced up by window. Solution: Special "stunt glass" designed to break easily and safely.

Problem 5: Keeping from being dazed and useless after going through the window. Solution: Practice. StuRat (talk) 18:26, 27 December 2010 (UTC)

Perhaps it could be done with a bungee jump rope. 92.29.122.99 (talk) 19:42, 27 December 2010 (UTC)

• This sounds like the perfect thing to suggest to the Mythbusters. — The Hand That Feeds You:^Bite 22:29, 27 December 2010 (UTC)

Great answers, thank you everyone! I'm not sure how to suggest anything to Mythbusters, but it could make a neat segment. – Kerαunoςcopia^◁_galaxies 02:31, 29 December 2010 (UTC)

Is the earth gaining weight?

I couldn't find an answer in the archives. But with my limited knowledge of science, with all the people being born and gaining mass throughout the centuries, shouldn't the earth be gaining mass? Or is the earth losing energy to each living person? I ask, because in the movie Houseboat, Cary Grant explains death to his son in terms of a pitcher of water that is poured back into the earth. I understood where the death of a person becomes the earth, but I don't understand where the mass of a born person comes from. – Kerαunoςcopia^◁_galaxies 08:42, 27 December 2010 (UTC)

Try to reproduce without ever eating, and then ask again. Feezo (Talk) 09:02, 27 December 2010 (UTC)

Yes. We eat plants, or eat animals that have eaten plants. The plants appear to grow from nothing (apart from a seed), but in fact they are grabbing carbon and oxygen from the air, where we don't really notice its weight or size. I always thought this was one of the more amazing things about plants when I first learnt about it. All that bulk in giant trees was once just air. HiLo48 (talk) 11:06, 27 December 2010 (UTC)

Energy that comes from the sun could be converted into mass. Then again, the same energy could be converting the Earth's mass into energy. An interesting idea. If we could calculate the amount of sunlight absorbed by Earth, then we could calculate an upper limit on mass gained. I think my mathematical modeling class would have handled this. ;) Magog the Ogre (talk) 11:28, 27 December 2010 (UTC)

It's a fairly easy calculation. The average insolation at the top of the Earth's atmosphere is 1366 watts per square metre. The Earth's radius is 6371km and its albedo is 0.367. The energy gained in a second is insolation*cross-sectional surface area*(1-albedo). In this case, we get 1.1*10¹⁷W. Divide that by the speed of light squared and we get about 3kg per second. --Tango (talk) 11:54, 27 December 2010 (UTC)

The Earth is also gaining weight through meteorites that are trapped by her.Quest09 (talk) 11:56, 27 December 2010 (UTC)

Magog and Tango's answers are ridiculous, Magog has turned E = mc² on its head and using it in the wrong way, and Tango is encouraging him. Energy radiating from the sun, does not turn into mass on Earth. That equation has to do with nuclear physics, far removed from the concept you're talking about. The Earth loses mass in the form of the lighter gasses in the atmosphere escaping the Earth's gravitational attraction, gasses like helium and hydrogen. On the other hand, the sun is adding the same gasses back by radiating the Earth with solar wind however, I don't know the net gain or loss of these gasses relative to the Earth. In addition to these, as Quest09 has said, space debris, like meteorites, continuously rain down on Earth. Material that makes up the biosphere is continuously being recycled. That, is live does, life takes a chaotic mess of matter, and with the use of energy from the environment, shapes it into something with complexity and order. Death releases the energy back into the environment, letting the order and complexity decay back into a natural tendency of chaos. A simple example of thermodynamic law of entropy. You ask where the mass of a born person comes from? Think of a brick wall, a brick wall does not grow wider by stretching the bricks, instead new bricks, made from fresh clay must be added to the wall. Similiarly, a person does not grow by stretching, new cells must by made by their body. These cells do not appear out of nothing, they are made from what the body can extract from the very food we eat. This applies to whether a person has been born or not. In simple terms, we are build from what we eat, don't take this literally, this is an oversimplification. For the unborn, who not yet eating for themselves, has their mother to eat for them, since they share a body for the time being. I hope this answers your question. --Plasmic Physics (talk) 12:42, 27 December 2010 (UTC)

Nope, Magog and Tango's answers are completely correct. Energy radiating from the sun most definitely does turn into mass. However the earth also radiates into space, and looses mass that way, and the two are in balance. The earth also gains mass from interplanetary dust, and meteors. Also from solar wind. It looses mass from gases escaping, and technically from radioactive decay in the core (as stuff decays it gets lighter, and the mass is radiated into space as heat). Overall I believe it's gaining mass. Plasmic Physics: e=mc2 works both ways. A stretched rubber band actually weighs more than a relaxed one, and I don't mean in some nuclear way - I mean if you had a scale to weigh it on, it would actually weigh more. Same for chemical reactions, and everything else. Ariel. (talk) 20:09, 27 December 2010 (UTC)

You probably mean that it loses mass. Even though, in this case, it's also true that it looses it unto the deep.... --Trovatore (talk) 22:35, 27 December 2010 (UTC)

I agree that there are all kinds of other factors that result in the gain and loss of mass, but sunlight being absorbed does add mass at approximately the rate I said (I think I miscalculated and it's actually more like 1kg per second, but that isn't important). If E=mc² then m=E/c², there is nothing wrong about that. The extra mass is because the total mass of a glucose molecule and oxygen molecule is greater than the total mass of the water and carbon dioxide that they were made from (see bond energy). The other factors may be significantly greater in magnitude, but that doesn't mean that what Magog and I have said is wrong. --Tango (talk) 13:24, 27 December 2010 (UTC)

Actually Tango's logic is exactly correct - but there is a fatal flaw in his arrangement. He only calculated incident radiation - and completely forgot to compute the net radiation - which is (roughly) "amount of input energy from Sun" - "amount of thermal energy radiated by Earth." This amount, called the net energy flux of Earth (or "Earth's energy budget"), is incredibly important as a parameter of planetary and climate science. In fact, when climatologists and planetary scientists discuss "global warming," they are trying to compute an exact value for the net energy flux - i.e., is more energy coming in than going out? (If so, the planet is warming). Most estimates of net energy balance place it around 1 to 3 watts per square meter; though there are huge debates about this. Some scientists even believe the net flux is slightly negative (and that Earth is actually cooling). Many scientists believe that human-created pollution can change the energy flux - mostly by affecting the chemical balance of the Earth's stratosphere (adding Carbon Dioxide, for example, and changing the incoming and outgoing radiation rates). In truth, the exact amount of net energy is hard to determine, and there are a lot of "fudge" factors; and defining the "edge" of the Earth is very hard (i.e., if the magnetosphere experiences a net warming but the rest of the atmosphere experiences a net cooling... has the planet warmed or cooled?) In any case, Tango's approach is valid - if there is a net change in the thermal energy, this will exactly follow the conventional relativistic equivalence between energy and mass - and does affect the gravitational mass of the Earth. But, because of the disparity between incident and net energy flux, Tango's 3 kg/second is off by approximately 3 orders of magnitude. As such, Earth gains far less mass from solar radiation of energy than it does by gravitational capture of micrometeorites. (That is a very real and measuarable effect that you can read about here: The micrometeoroid mass flux into the upper atmosphere... (GRL 2001), describing quantitative RADAR measurements (from Arecibo Observatory) of meteorite rate. Nimur (talk) 13:44, 27 December 2010 (UTC)

The mass of the Earth generally does not change on short timescales because the mass that any organism gains is aquired from other organisms or compounds within the Earth's biosphere. Since we don't purposefully eat micrometeoroids, our mass gained comes entirely from the Earth, and returns to the Earth when we decay. The extra mass gained from meteoroids and meteorites is small but accumulates over time, though this too is likely balanced out by the ejecta that leaves the Earth's gravitational pull during periodically much larger collisions. ~AH1^(TCU) 17:37, 27 December 2010 (UTC)

I don't know about ejecta leaving Earth. Wouldn't any meteor large enough to do that also rupture the Earth's crust and destroy all life on Earth ? There is a theory that the Moon was formed that way, in the early days of the solar system, but nothing since then, I believe. StuRat (talk) 18:16, 27 December 2010 (UTC)

The flux of micrometeorites and interplanetary dust is about 2.5 ×10⁶ kg/year [1]. If it were a single rock, that would correspond to about a 10 m cube / year. I don't think the rate of ejecta is anywhere near that large. Dragons flight (talk) 19:21, 27 December 2010 (UTC)

My point was entirely that all food that gives mass to life on Earth comes from the sun; thus I was using the e=mc2 function. Obviously, the function will heavily overestimate, especially in view of the fact that much of the energy from the sun is defracted back into space (most, I believe; there just aren't enough greenhouse gases here). And, like AstroHurricane has pointed out, we don't actually eat astroids, so it seemed tangential to the OP's question. Magog the Ogre (talk) 21:19, 27 December 2010 (UTC)

Sure we eat asteroids, after they fall to Earth and mix with the other soil, which is absorbed by plant roots, eaten by animals, and finally us. And "...all food that gives mass to life on Earth comes from the Sun" is just wrong. Pretty much only hydrogen and helium come from the Sun, while most of our bodies are made from heavier elements from supernovas which happened billions of years ago, before the formation of the solar system and Earth. StuRat (talk) 22:04, 27 December 2010 (UTC)

The energy comes from the sun, I meant. Magog the Ogre (talk) 22:32, 27 December 2010 (UTC)

Yes, most of the energy comes from the Sun, but there are some organisms that get their energy from volcanic vents on the ocean floor and geysers, etc. StuRat (talk) 23:30, 27 December 2010 (UTC)

A point I find fascinating is regarding how trees and plants grow mostly out of "thin air". Because of conservation of mass, when you burn a tree you are left with ashes which are pretty light, but if added the mass of ALL the gasses that escaped while you were burning the tree, you would end up with the same mass as the tree you started with! I still think that's pretty incredible. Vespine (talk) 23:20, 28 December 2010 (UTC)

I think most of the mass of plants comes from the ground, in the form of water (and a few minerals) absorbed through the roots. StuRat (talk) 00:52, 29 December 2010 (UTC)

There's a lot of discussions about this on the internet, (search "where does the mass of a tree come from"). My impression of it is that most come to the conclusion that "the ground" is not correct and that most of the mass is from the carbon extracted from the air. Vespine (talk) 01:17, 29 December 2010 (UTC)

But most plants are around 80-90% water, which contains no carbon. StuRat (talk) 07:01, 29 December 2010 (UTC)

Yes, I suppose it is, if you look at it that way. However, I don't think it is unreasonable to argue that the water is "drawn up" into the tree, not that the tree is actually made out of water. The tree is made out of wood which is cellulose, lignin and other organic carbon containing molecules. Vespine (talk) 21:38, 30 December 2010 (UTC)

The water is both within and between the cells of a plant, so I certainly consider it to be part of the plant, just like I consider the water in my body to be part of it. But, then again, your definition allows me to claim I weigh under 100 pounds, so I'll tell everyone I just lost a lot of weight. :-) StuRat (talk) 01:26, 31 December 2010 (UTC)

Thanks everyone for your responses, this is exactly what I was looking for. I didn't realize I was essentially asking "Where does the mass of a tree come from?" but I sort of had to wonder about the ethereal part of the human soul, but no one mentioned it (or if billions of souls would even register against billions of human bodies). Still, I think this is all fascinating, thank you! - Kerαunoςcopia^◁_galaxies 02:30, 29 December 2010 (UTC)

Yowzer! Since science has absolutely no evidence of "souls", even with our most accurate instruments, I'd say we can confidently say that even if there is such a thing as a soul, they do not add to the "mass" of the earth. Vespine (talk) 03:39, 29 December 2010 (UTC)

It was just a mere curiosity : ) – Kerαunoςcopia^◁_galaxies 06:26, 29 December 2010 (UTC)

voilation of parity in beta decay

question:how parity is voilated in beta decay? — Preceding unsigned comment added by Awanishkt (talk • contribs) 11:13, 27 December 2010 (UTC)

Is that a homework question? If not, can you elaborate a bit for our edification? Magog the Ogre (talk) 11:29, 27 December 2010 (UTC)

I guess voilation is a misspelling of violation. I don't know the subject but the Google search violation parity "beta decay" gives hits, for example Parity (physics). PrimeHunter (talk) 14:33, 27 December 2010 (UTC)

I kind of like the root word "voilà", meaning "...to suggest an appearance, as if by magic": [2]. StuRat (talk) 18:06, 27 December 2010 (UTC)

People getting fat

So now it turns out both the British [3] and Australians are getting fat too. It has by no means been limited to the US, premature reports aside. In the US, it's fashionable to blame it on high fructose corn syrup, but I haven't a clue if that (uneconomical but for poor legislation) concoction is even available in Britain or Australia. It's clearly something to do with lifestyle or wealth. What in the world could be the cause of all this? Magog the Ogre (talk) 11:25, 27 December 2010 (UTC)

McDonald's, Subway, Aldi, Burger King, Monosodium glutamate... Always read the criticisms sections. It is ddefinately not only high fructose corn syrup (although I haven't read the article) — Preceding unsigned comment added by Eu-151 (talk • contribs) 11:51, 27 December 2010 (UTC) --Eu-151 (talk) 11:52, 27 December 2010 (UTC)

Why would monosodium glutamate make you fat? Some people claim that it is unhealthy, but it is only a salt, and I suppose with little content of calories. Quest09 (talk) 13:25, 27 December 2010 (UTC)

I agree. MSG may have health implications (I haven't looked into it), but it doesn't make you fat. --Tango (talk) 13:27, 27 December 2010 (UTC)

MSG tends to be in foods that do make you fat, and makes them more appealing. That's the theory, anyway. - Jarry1250 ^{[Who? Discuss.]} 13:51, 27 December 2010 (UTC)

And also it's supposed to be an appetite stimulant. That is, even if you got it in an IV drip, it would still make you hungrier. (I make no claims that this is true, only that it is one theory.) StuRat (talk) 17:52, 27 December 2010 (UTC)

I don't think we use HFCS much here in the UK. It doesn't matter what the source of the calories is. If you consume more calories than you use, you will get fat. It is that simple. People are getting fat because they are eating too much and exercising too little. There is nothing more to it (you can try and explain why those things are happening, of course, but blaming it on particular types of food isn't going to help). --Tango (talk) 13:27, 27 December 2010 (UTC)

Specific kinds of food could be an issue here. If something is a calorie bomb, you can ingest lots of calories with just drinking or eating a little of it. Quest09 (talk) 13:37, 27 December 2010 (UTC)

This article lists some research into it and provides some explination:Division of Nutrition and Physical Activity. Research to Practice Series No. 2: Portion Size. Atlanta: Centers for Disease Control and Prevention, 2006. The UK and Down-under are copying the American food industry -so the problem spreads.--Aspro (talk) 15:04, 27 December 2010 (UTC)

The lack of exercise in modern society, and the lack of a standard physical education system (!) in 49 American states must play a role as well. ~AH1^(TCU) 17:33, 27 December 2010 (UTC)

I agree that consuming too many calories and burning too few is the problem. Consuming too many is a result of large amounts of unhealthy food being provided cheaply and conveniently, as by fast food restaurants, vending machines, and pre-packaged processed junk food, like chips/crisps. If you had to pay a lot for potatoes, then had to make the fries/chips/crisps yourself, then clean the pots, pans, and dishes, you would tend to eat a lot fewer.

The Internet seems to be a big factor in reducing exercise, but perhaps there's some hope in Wii-type games, which require participants to exercise in order to win. Perhaps one day we will be running marathons on tread-mills surrounded by wide-screen TVs, with our friends on the screen beside us. Rising gasoline/petrol prices may also encourage us to walk or bicycle more. StuRat (talk) 18:01, 27 December 2010 (UTC)

People eat more and more food that is high in fat (main culprit), and also sugar. It has high calories but little bulk or fibre, so even when you've eaten too many calories you still do not feel full or satisfied. People do not eat enough fruit'n'veg which does fill you up with few calories. Modern food has become too readily available, too cheap, and over the years the food retailers sell has evolved to become more and more delicious. I remember when I was a child rather long ago, there wasnt any convenience or junk food apart from fish and chips, and I was slim. A practical means of losing weight may be to eat as much fresh fruit'n'veg as you can, as then you won't have any room left over for junk food - at least that's what I've found. 92.29.122.99 (talk) 19:32, 27 December 2010 (UTC)

I think people are getting fat because they are not eating enough fat. People are eating carbohydrates instead, but you need more of them to give a full feeling, so people eat too much. If they added some fat to the meal they would feel full earlier and eat less. And especially if they chose fats with good components (polyunsaturated, etc). Ariel. (talk) 19:57, 27 December 2010 (UTC)

What makes you feel full is bulk and weight, and fat has neither of those. Eating more fat would give you too many calories without making you feel full. If you have satisfied your hunger through eating fats, then you will have eaten far too many calories. Saturated fats, mostly of animal origin, are generally considered to be particularly bad for you. 92.24.187.63 (talk) 10:59, 28 December 2010 (UTC)

With all due respect to everyone, only a few have you have directly addressed what is different now than what existed 20 years ago. Of course eating fast food can make someone fat, but that was true back then too. And as for the argument for the internet: I find it entirely unconvincing: there were Nintendos and television back then too. And not that many people spend all day in lounging in front of the internet that wouldn't have lounged before. Magog the Ogre (talk) 21:21, 27 December 2010 (UTC)

TV and earlier video games had their effects, too, and obesity was higher 20 years ago than 100 years ago. However, TV and any particular video game each get dull after a while, while the Internet represents an almost infinite range of forms of entertainment, all available from an easy chair (that's where I am right now). They also eliminate the need to exercise in order to have social interaction, which is a big draw for teens. As for the price of fast food, it's barely changed, in dollars, over the last 30 years, despite inflation in ever other sector (except maybe electronics). A hamburger could be had for a bit under a dollar then, and it still can be, now. Meanwhile, the price of, say, a car, has gone up maybe 10x. StuRat (talk) 21:50, 27 December 2010 (UTC)

Not all high calorie foods are bad--it is only bad if you do not use the calories and they accumulate. --Chemicalinterest (talk) 21:55, 27 December 2010 (UTC)

...and whether the food also contains important nutrients or just "empty calories". StuRat (talk) 21:58, 27 December 2010 (UTC)

What makes you fat is simply: eating too much. When I visited Disney Florida (I'm South African), the servings were enormous and the Americans were polishing them off and going for dessert afterwards! Who eats a full breakfast of pancakes and sausages and then a whole cheesecake - fat people! We on the other hand, despite vagabond stares from locals, shared meals amongst ourselves and stuck to simple bread or cereal breakfasts like the way we eat at home. Another simple indicator is the amount of fries served at Macdonalds... in the USA a small fries is MUCH larger than the one they serve in Thailand... and I didn't see any fat people there (although I believe the east is heading in the wrong direction due to wetern eating influence). We do have an obesity problem here with certain sectors of the black population who eat too much phutu. It is less about the quality of food; it is the quantity. It is in local culture that says 'to be fat means I am well to do' and so they see obesity as an acceptable African culture thing. Sandman30s (talk) 12:16, 28 December 2010 (UTC)

And yet again, sandman, that doesn't address what's different now than what was 20 years ago. Nor does this anecdotal story explain why countries other than the US are getting fat at comparable levels. Magog the Ogre (talk)

The UK article you (Magog) linked to says "Scientists put the average weight rise of 7.7kg (16.9lb) down to men eating more calories and taking less physical exercise than 15 years earlier." also, specifically referring to reduced exercise in men. "The problem is really how people are getting around. They are driving more, cycling less and more likely to be employed in a sedentary job." "Physical activity is slowly being removed from day-to-day life." (Dr Peter Scarborough, senior researcher in public health at Oxford University)
I think that pretty much sums up the problem. Several factors are involved, that add up to what many would likely call 'lifestyle'. Longer working hours (likely more common than 20 years ago?) has not been mentioned so far. People who work longer hours are perhaps more likely to turn to fast food, Convenience food or TV dinner/s'microwave meals' to save time 'wasted' cooking. The ease with which a bought pre-prepared meal can be heated in a microwave oven, may be a factor that has not been fully addressed. See Fast food#Health issues, Convenience food#Nutritional issues, TV dinner#Health concerns - 220.101 talk^\Contribs 01:28, 30 December 2010 (UTC)

That is an interesting point. I hadn't thought of it. And yet, when I look at pictures of my parents 20-30 years ago, it's clear that everyone was skinnier back then. I can't possibly see how a little extra work could cause that, unless for some reason the lack of sleep is can affect weight (which I know it's done to me in the past, interestingly). Several friends and I noticed recently when we had to quit work, that we all lost several pounds, yet none of us thought we ate too much in our sedentary job. Magog the Ogre (talk) 08:28, 30 December 2010 (UTC)

There is an adenovirus (serotype 36) which may be implicated, but the shrinking middle class (growing number of people not sure how they're going to pay for the next heat and shelter payments) combined with advances in agriculture, fertilizers, irrigation, and pesticides producing an over-abundance of subsidized food for the poor is mainly to blame according to http://equalitytrust.org - do you agree? 208.54.5.50 (talk) 14:37, 30 December 2010 (UTC)

Actually Magog, there is supposed to be a strong link between staying up late (editing wp for example! ;-) ) and/or poor sleeping and weight gain! (possibly no more than scoffing bags of chips/crisps and chocolate etc. late at night. "empty calories" as StuRat said. ) I don't have a link at hand, but it is something to look into. - 220.101 talk^\Contribs 04:23, 31 December 2010 (UTC)

ps. I certainly weigh more than 20 years ago! The world population, especially in the 'developed' countries is supposed to be aging. I wonder if that factor has been allowed for? Do people tend to put on weight as they age?, I would think they would 'tend' to lose it even later in life.220.101 talk^\Contribs 04:41, 31 December 2010 (UTC)

Blister

What is the purpose of Blisters? The article doesn't say —Preceding unsigned comment added by 174.139.241.18 (talk) 14:10, 27 December 2010 (UTC)

They don't really have a purpose (eschatological rumination aside). They are an unfortunate symptom of damage to skin; they are the result of fluid pooling and becoming trapped between layers of skin. You might like to read about skin and see the diagrams in epithelium to understand the structure of human skin; you can see that if a lower layer is damaged (but an outer layer is intact), it is possible for lymph and other fluids to become trapped. Nimur (talk) 15:50, 27 December 2010 (UTC)

There is an entire class of vesiculobullous skin diseases, such as pemphigoid, in case you're interested. DRosenbach ^{(Talk | Contribs)} 17:31, 27 December 2010 (UTC)

They protect your skin from whatever caused the blister. It's like wearing padding, but the body is making its own padding. --Tango (talk) 22:11, 27 December 2010 (UTC)

No Tango, I don't think that is correct. Nimur above has pretty much explained it. Blisters are an incidental result of some sort of trauma, they occur under specific circumstances and if these circumstances are exceeded then the blister no longer protects. For example think about running in ill-fitting shoes, first you'll get a blister and then it will burst. Think about a burn, a slight burn may cause a blister but more heat will just sear the skin. What you are thinking about is a callous, a thickening of the skin developed after repeated rubbing or pressure over a sustained period. However this is more an incidental effect than any sort of 'deliberate' protection. Caesar's Daddy (talk) 08:42, 28 December 2010 (UTC)

I don't think they're "padding", but I do think the integrity of the skin on top of the fluid, as long as it lasts, protects the wound and gives it a little time to start healing before it has to deal with bacteria. By the way, callous is an adjective; you probably mean callus. Compare also mucous versus mucus and phosphorous vs phosphorus. --Trovatore (talk) 09:52, 28 December 2010 (UTC)

Well, our article agrees with me. Blister says: "This fluid cushions the tissue underneath, protecting it from further damage and allowing it to heal." (1st paragraph of "Causes" section). --Tango (talk) 16:32, 28 December 2010 (UTC)

Materialism, Reductionism and Determinism in science

Hi. I have questions about the following methodologies common in science:

Could materialism be seen as a useful way to quantificatively objectify reducible concepts within the focus of modern scientific study, rather than a systemic refutation of any possibility of an existence outside the material realm?

Could reductionism be seen as a useful way to determine the workings of each microscopic part of a larger system, rather than putting the overall holistic nature of the entire macroscopic complex system into irrelevance?

Could determinism be seen as a useful way to find a causal mechanism in retrospect of each material stage of a phenomenon, rather than a prior assumption of premediated certainty in event occurrence in a set mechanism?

Thanks. ~AH1^(TCU) 17:30, 27 December 2010 (UTC)

I think the answer to all of the above is "yes," and that such "positive" interpretations are built into the methodologies themselves. For in each of these, science recognizes that their core definitions are not necessarily known a priori. For example, with "materialism," it is true that it denies the existence of phenomena outside of the "material realm," but it has openly recognized that the definition of the "material realm" can and does change. It did not used to include such things as radio waves, for example, or dark energy, both of which have been admitted to the "material" as they became understood in terms which allow for study, replication, and etc. What is usually defined as "immaterial" are things which cannot be measured, replicated, "made reliable," etc. Science is overjoyed (in the long run, anyway) to realize that its definitions for these sorts of things are incorrect — indeed, nearly every scientific revolution has been based on such a rumbling of these sorts of foundations. (In the short run, of course, controversies are common.) --Mr.98 (talk) 17:46, 27 December 2010 (UTC)

So materialism cannot and does not, by itself, refute the possible existence of anything immaterial? In this case, is it correct to say that to do so would make the concept prove itself (self-materializing)? ~AH1^(TCU) 18:01, 27 December 2010 (UTC)

• Well, I guess it could be, but really: "In philosophy, the theory of materialism holds that the only thing that exists is matter; that all things are composed of material and all phenomena (including consciousness) are the result of material interactions."
• "Reductionism can either mean (a) an approach to understanding the nature of complex things by reducing them to the interactions of their parts, or to simpler or more fundamental things or (b) a philosophical position that a complex system is nothing but the sum of its parts, and that an account of it can be reduced to accounts of individual constituents." I think the position (b) is what you're questioning, right? So, just go with (a) if you want. :)
• No, strong determinism is the belief that given perfect and completely detailed knowledge of an information-closed system, the behavior of that system can be determined at and for all times. WikiDao ☯ (talk) 18:17, 27 December 2010 (UTC)

Have you read the Wikipedia articles Materialism, Reductionism and Determinism ? I think your questions "Could xxx be seen as... invite comment on what you propose as definitions of these -ism terms. None of them encapsulates The Scientific method. Instead they are selective characterisations of the Philosophy of science.

• Materialism is the attitude that matter is the primary component of reality and mind or spirit are secondary consequences. It does not "refute" the latter but takes it as axiomatic that they are products of matter acting on matter. "Quantificatively" is not an English word.
• Reductionism is the position that every concept or theory will be explicable in terms of another lower level concept or theory. The nature of a complex system is not thereby declared irrelevant, rather it is potentially fully sythesizable from the lower level theories. Your tautological adjectives "overall holistic entire macroscopic" seem equivalent to me.
• Determinism is the assumption that events are predefined with inevitable certainty in a causal chain. "Premediated" is not an English word but if you mean "premeditated", that term introduces the theological concept Predestination that is not essential to determinism. Cuddlyable3 (talk) 23:54, 27 December 2010 (UTC)

Determinism is certainly not a "useful way to find a causal mechanism", as the original poster suggested. At most, it postulates that such a mechanism exists; it doesn't help you find it.

But even that much is not clear. That sounds more like mechanism than determinism. As I understand it, determinism per se does not require that events be determined causally, but only that they be determined, period. If the future is set in stone, but not for any particular reason, that's still a deterministic situation. --Trovatore (talk) 09:58, 28 December 2010 (UTC)

And yet our article about Determinism states it is the concept that events are bound by causality and the universe is fully governed by causal laws (my bolding). Cuddlyable3 (talk) 13:11, 28 December 2010 (UTC)

Actually it says "specifically causal determinism". This is a flaw in the article, frankly. If it wants to be about causal determinism, it should be moved to causal determinism.

In somewhat contradictory mode, further down in the article, at least two non-causal (or at least not-necessarily-causal) variants of determinism are described, namely fatalism and necessitarianism. --Trovatore (talk) 18:12, 28 December 2010 (UTC)

there was blizzerd today and it looks like a very cold winter... THEREFORE THERE IS NO SUCH THING AS GLOBAL WARMING

that is what my friend says. this does not sound right to me, but I do not know how to counter his boisterous claims. What should I tell him?--Voluptuous Nature (talk) 19:06, 27 December 2010 (UTC)

Tell your friend that weather is not climate. The climate is, and has been, changing. A single weather event is exactly that. See Climate change and other articles linked therefrom, including Global warming. --LarryMac | Talk 19:10, 27 December 2010 (UTC)

but lets say there were 3 very cold winters in a row. is that weather, or is it climate? if that hapened, would it cast doubt on global warming?--Voluptuous Nature (talk) 19:13, 27 December 2010 (UTC)

Weather is local: climate is global. In individual areas, the local weather can indeed be colder under general climate change scenarios. It's worth noting that climate change research predicts an increase in intense weather activity: i.e., hurricanes/typhoons/cyclones in summer, and blizzards in winter. Winter is not going to go away, but it can get shorter, and can feature more storms - blizzards like the current U.S. East Coast storm are often the product of a collision of cold air with warm, moist air. More warm moist air + a cold boundary = snowstorm. Acroterion _(talk) 19:19, 27 December 2010 (UTC)

OK thanks. That is what I will tell my dumb friend :-D--Voluptuous Nature (talk) 19:26, 27 December 2010 (UTC)

There was an editorial in the New York Times yesterday on just this very subject. I'm no climate scientist, so I'll withhold my own judgment, but it is an interesting argument. --Mr.98 (talk) 19:46, 27 December 2010 (UTC)

If you want to impress your "dumb friend," explain to him that measuring the temperature on Earth is a very complicated process. The "Global Temperature" represents the zero-frequency component of the monopole moment of a spherical harmonic decomposition of a model of the complete global surface temperature as a function of time; and that like all planetary parameters, any effort to describe global-scale behaviors with single numbers is inevitably doomed to exclude high-frequency components (such as diurnal variations, short-duration weather phenomena, and local geographic variations). As such, a powerful and cold winter-storm that is local in geographic extent and short in duration will not be effectively captured in the "average global surface temperature," which most scientists believe has demonstrably trended towards the warmer side over the past hundred or three hundred years. Also, direct your friend to NOAA's explanation about mapping the global temperature, their global maps of ocean-temperatures, and these major research projects, NOAA Pathfinder and NASA's MODIS spacecraft instrument (we also have an article on MODIS). That spacecraft program was specifically designed for the purpose of monitoring global temperature, has flown on multiple spacecraft, and its data has been studied in great detail by thousands of scientists worldwide. In fact, you and your friend can even plot the global temperature data yourself with a variety of data-processing parameters, using NASA's online temperature plotting tool. If your friend disbelieves the data or the results, he/she can finance and launch his own global climate measurement apparatus and try to collect contrary data. Nimur (talk) 20:19, 27 December 2010 (UTC)

I think your redlink monopole moment should be a link to the article Multipole moment. But is the zero-frequency component of the harmonic decomposition any different from a simple average taken over the sampling time? I would think that near zero order components would be of more interest for extrapolating beyond the sampling time. Cuddlyable3 (talk) 19:31, 28 December 2010 (UTC)

Also note that large volumes of snow may make it look cold, but more snow actually falls when the temp is around freezing. When the temp is very cold, like in Antarctica, very little new snow falls. (Yes, there's lots of snow on the ground there, but that's because it never melts and builds up over thousands of years.) StuRat (talk) 21:41, 27 December 2010 (UTC)

If one wanted to frame the issue slightly more humorously: http://www.youtube.com/watch?v=TQlHaGhYoF0 - Jarry1250 ^{[Who? Discuss.]} 22:00, 27 December 2010 (UTC)

Climate science is at least as complicated as knowing how every detail of every component of a car works. Someone who can start the car and turn the sterring wheel is a long way from this level of understanding. HiLo48 (talk) 22:10, 27 December 2010 (UTC)

People who say this will invariably dismiss the next heatwave as merely a weather phenomenon. I'd bet your friend will do the same. Imagine Reason (talk) 14:47, 28 December 2010 (UTC)

The "warming" part of "Global Warming" is not supposed to mean that the entire earth with cook like it's in the oven. We're talking about a warming effect of a couple of degrees. In and of itself, that warming wouldn't be an issue at all, (You wouldn't notice it amid day-to-day variations in temperature.) but it's believed that by pushing the global average temperature up a couple of degrees we're going to screw up weather paterns, ocean currents, ice-caps, etc. APL (talk) 18:02, 28 December 2010 (UTC)

The nor'easter that hit the Eastern US was the December 2010 North American blizzard, and strengthened over the Gulf Stream which provided its extra boost of energy. Cold weather and extra snow do not disprove global warming any more than it supports the anthropogenic theory. See Arctic dipole. Certain mechanisms can lead to colder winters, such as intrusions of the Polar vortex due to rigid blocking patterns. Reduced Arctic sea ice from Arctic shrinkage can cause warm air to fill the Arctic in winter, forcing its coldest air over the continents where it's ususally warm. La Nina, the current phase of ENSO that we are in, typically results in warmer weather for the Southeastern United States and makes strong nor'easters such as the recent one very rare. Other factors such as a slowing of the Gulf Stream can bring colder winters to much of North America and Europe, as we have perhaps seen recently. Natural oscillations such as the North Atlantic Oscillation and Pacific-North American teleconnection pattern are also important factors. Remember that climate is a complex system that requires holistic processing (What, no article?!) to comprehend, and a small nudge in this system can have astoundingly complex outcomes. ~AH1^(TCU) 21:48, 30 December 2010 (UTC)

But if measuring the temperature of the earth is such a complicated process, how are the simple measurements from 100 years ago any good? Googlemeister (talk) 15:41, 31 December 2010 (UTC)

The instrumental temperature record itself, as well as the satellite temp record are not measuring a complex process. These only measure an average temperature of the Earth by compilation, and measurements from a century ago may well be as accurate as those today. It's the computer models that have the hard task of calculating future changes in this system, and the interactions within this system that create uncertainties. ~AH1^(TCU) 16:45, 1 January 2011 (UTC)

How many years off are we from cell phones working as well a regular phones did 40 years ago?

There is no doubt that cell phones can do things that traditional landline phones cannot. Don't get me wrong, I like my cellphone (though sometimes I worry that it gives me cancer in my private parts, but that is another question entriely).

But here's the thing.... before cell phones were invented, regular phones used to work great. You could hear the person on the other line, the call would stay connected until one of you hung up, you could go deep underground and as long as there was a phone down there, you could still hear the other person.

How far away are we from cell phones being equally reliable?--Voluptuous Nature (talk) 19:12, 27 December 2010 (UTC)

Well, the part about being underground is always going to be a sticking point; a land line phone only requires, well, a land-line to work while your cell phone requires a connection to a cellular signal, usually from a tower. I expect that we'll see a continual improvement in cell phone coverage and there will likely be some clever ways exploited to increase the penetrating power of the signals, but it's just not ever going to be as good a connection as a physically solid cord. Similar arguments take place in the popular debate over cable versus satellite television. Matt Deres (talk) 19:37, 27 December 2010 (UTC)

But could we put little cell phone node things in every wall, even undergorund, just like every wall today has an electrical outlet and these cell phone nodes would be somehow wired to actual cell phone towers. IS this a plausible idea?--Voluptuous Nature (talk) 19:49, 27 December 2010 (UTC)

WP:OR - Qualcomm, a technology company that owns/designs most of the electronics that make your cell phone work, has been investigating "micro-towers," "nano-towers", and "pico-towers," with the ultimate goal of making 100% cell-phone coverage cost-effective. The idea is to use a large tower for covering most of the city, and then using progressively smaller devices (all the way down to a "femto-tower" the size of your current 802.11 router device) to fill in any radio-shadows ("blackout areas" without coverage) - even single rooms. You can read their public white-paper, LTE Heterogeneous Networks (in reference to 3G LTE), which describes the strategic motivations and some of the technical obstacles to this development. "Since radio link performance is approaching theoretical limits with 3G Enhancements and LTE, the next performance leap in wireless networks will come from the network topology." In laymans' terms, the wireless part of the radio connection can't get any better - but we can connect up the radio-links in a more intelligent, efficient way. I wouldn't be surprised if other major wireless technology companies (at least one other) were similarly investing in this area. Nimur (talk) 20:31, 27 December 2010 (UTC)

In the UK, Vodafone offer mini cell phone towers to customers that cannot get a signal on their network. SmartSE (talk) 00:20, 28 December 2010 (UTC)

A chain is only as strong as its weakest link. Kittybrewster ☎ 20:29, 27 December 2010 (UTC)

Only if it is linear. If it is redundant, then it is much stronger than one weak link. --Mr.98 (talk) 00:29, 28 December 2010 (UTC)

I've noticed they seem more interested in pushing new features (like streaming video) than in improving basic service. I agree with the poster that I'd be much happier if I could always get a good signal, and a loud volume, than if I had games and video on my phone. One thought that comes to mind is car phones. They used to have their own antennas and could be as large as needed, but now we use our cell phones in the car instead. Why couldn't the car have a "booster" hooked up to your cell phone, with a proper antenna and power source, so you could still use it in weak signal areas ? (Using a hand's free phone, in the car, of course.) They do seem to have figured out how to plug the cell phone into the car speakers, both to mute the radio and to get a volume you can actually hear, while driving. StuRat (talk) 21:31, 27 December 2010 (UTC)

I believe the research into the use of mobiles in cars indicates that it's the conversation itself that causes the inattention to the road and consequent danger (equivalent to being drunk to some degree or other), not the use of a hand-held device. "Never use a phone when driving" is the advice that should be given, IMHO. (As is "Never use apostrophes in plurals") AndrewWTaylor (talk) 21:57, 27 December 2010 (UTC)

I was thinking it was a contraction for "hand is", as in "my hand's free". StuRat (talk) 23:21, 27 December 2010 (UTC)

To help people who can't or won't follow that good safety advice there are countries where using a hand-held phone while driving is illegal. Wikipedia has an article about that small text item. Cuddlyable3 (talk) 22:45, 27 December 2010 (UTC)

Cellular phones use radio signals. And radio is subject to interference from a variety of sources. You can improve radio transmission & reception by adding more towers, and improving the technology in cell phones for detecting weaker signals... but you'll never be as reliable as a wired telephone. There's a similar issue with computers using Ethernet cables verus WiFi signals to connect to your Internet router: the physical cable is almost always going to have a cleaner, faster signal simply because it's subject to far less interference. — The Hand That Feeds You:^Bite 22:35, 27 December 2010 (UTC)

It is almost certainly true that wireless systems will never be superior to wired systems. However, when it comes to phone technology they don't really have to be. For the purposes of the question, it is basically sufficient if the wireless system is sufficiently clear, fast, and reliable that a human being couldn't tell the difference between a wireless call and a wired one. It seems plausible that with enough cell receivers and a very robust network design, that one might achieve that someday. However, I would observe that people probably care more about the difference between "no signal" and an "okay call" than the difference between an "okay call" and a "great call". Hence cell providers probably rationally try to focus on coverage rather than quality. Dragons flight (talk) 10:29, 28 December 2010 (UTC)

I think it's safe to say never. If they would, it would have been within a decade of their widespread use. the reality is, physical limitations cannot always be overcome with technology. Plus, if you notice, the vast vast vast majority of development goes into new features that are not traditionally part of "telephone" service. Infact, i dont think voice quality has changed one bit since the introduction of 2G digital service. everything else has focused on improving data and hardware/software interface and capabilities, not the call quality at all. Roberto75780 (talk) 11:05, 28 December 2010 (UTC)

And coverage is always restricted to where the companies "think" people will be. If I had a pound for every time the phone shows "no signal" (and I mean none at all, from any of the four suppliers!) whilst I boat along the UK canals, I would be a rich man...  Ronhjones  ^(Talk) 17:29, 29 December 2010 (UTC)

Smoke when a candle blows out

I had a plain old wax candle burning cleanly and emitting virtually no visible smoke and then when I blew it out there was quite a bit. In general at a layman's level, why was there virtually no smoke during the burning and why did smoking start as the flame died? Is it because the matter that would have become visible smoke was fully reacted into an invisible product while the flame was providing energy to do so?

Candle getting blown out

Thanks. Peter Michner (talk) 20:45, 27 December 2010 (UTC)

Yes, I think that is basically correct, and see also Visible and invisible particles of combustion. WikiDao ☯ (talk) 20:53, 27 December 2010 (UTC)

(ec) Yes, that's about right. During steady state (before you blow the flame out), the flame gets its fuel from heated paraffin that evaporates, and its oxygen diffuses in from the air; but the flow of gases is laminar (smooth) and the result is a well-mixed fuel-to-oxygen ratio. When you blow out the flame, the chemical reaction doesn't stop immediately - there's a brief period of turbulence. During this time, the fuel and oxygen are not well mixed, and the result is more soot and unburned paraffin vapor. This is followed by a slow smoldering of any remnant paraffin and the evaporation of a little bit more wax (which is briefly still hot enough to vaporize, but not hot enough to combust - so it floats away as "smoke"). Those two stages are what you see as visible gray smoke in a candle. Nimur (talk) 20:56, 27 December 2010 (UTC)

You didn't ask, but the way to keep your air from being polluted with candle soot is to cover it and leave it covered. The soot will still be produced, but will deposit on the cover and candle instead of on your walls and in your lungs. StuRat (talk) 21:23, 27 December 2010 (UTC)

It's mainly (flammable) paraffin vapor. Old magic trick, blow out the candle, put a lit match in the "smoke" and the match flame "jumps" down to light the candle. PЄTЄRS J VЄСRUМВА ►TALK 21:27, 27 December 2010 (UTC)

I don't like the smoke, so I always pinch out the fire instead of blowing it out. You can lick your fingers first if you want. The smoke is mostly unburned carbon and some hydrocarbons, because the flame isn't hot enough to burn them. When it's a normal fire it's much hotter. Ariel. (talk) 21:59, 27 December 2010 (UTC)

Yeah, this is why churches and other places that use candles for light have candle snuffers for putting out the flames. Very convenient, though you have to clean the wax & soot off the inside of the snuffer bell eventually... — The Hand That Feeds You:^Bite 22:39, 27 December 2010 (UTC)

Meter

Why is a meter the distance travelled by light in 299,792,458^-1 seconds? Why didn't they just make it a clean 300,000,000? Why did they pick that value at all? —Preceding unsigned comment added by 92.251.255.12 (talk) 22:54, 27 December 2010 (UTC)

The meter already had a value. Originally it was supposed to be one ten-millionth of the distance from the equator to the pole. Later, it was standardized as the length of a particular artifact held in France. Measurements defined by artifacts are undesirable for reasons that I hope are obvious, so they found a way to get rid of them for everything except the kilogram, but they didn't want to actually change the length of a meter, or at least not by an amount that anyone would reasonably notice. --Trovatore (talk) 22:59, 27 December 2010 (UTC)

... and, in fact, the metre has never changed its size since the first (mis-)measurement. Each redefinition has just improved the accuracy with which the length can be realised in practice. Imagine the confusion a redefinition would cause with some still using the old metre and some adopting the new metre (we can't even agree on the spelling!). They picked that value because it was the average of the most accurate measurements based on the previous definition, which was in turn chosen for the same reason ... (etc.) Dbfirs 00:02, 28 December 2010 (UTC)

Wikipedia has an article about the History of the metre (spelled that way at its historical French origin in 1790). Nearly two centuries passed until the meter was re-defined in terms of time and the speed of light in space. The latter is an absolute physical constant, while time can be measured with greater precision than the inevitably uncertain duplication of mechanical standard meters. Thus the definition adopted in 1975 has the purpose of prescribing a more stable and repeatable implementation of the existing standard meter, not of substituting a different meter for the sake of getting a round number in decimal arithmetic. Cuddlyable3 (talk) 00:22, 28 December 2010 (UTC)

The original spelling was not the British "metre"; it was the French "mètre". --Anonymous, 09:09 UTC, December 28, 2010.

Well of course it does have such an article ;-) hydnjo (talk) 00:51, 28 December 2010 (UTC)

If you write metre as meter, then you are referring to a gas-meter or an electricity-meter. 92.24.187.63 (talk) 11:10, 28 December 2010 (UTC)

Er .. no. If I write "meter" I am referring to a measuring device, but it is plainly the case that many people write "meter" to refer to the unit of length so your claim is contrary to fact. --ColinFine (talk) 17:34, 31 December 2010 (UTC)

"They could round it up to 300,000,000 s^-1, but then the length of a second has to be shortened from 1 s to 0.999,308,193 s. --Plasmic Physics (talk) 11:34, 28 December 2010 (UTC)

Would that make me older? HiLo48 (talk) 11:50, 28 December 2010 (UTC)